The present invention relates to a reciprocating type internal combustion engine for use as a driving unit in automobiles, motorcycles, construction machines, agricultural machines, light airplanes, ships, generators, etc., as well as a compressor and a pressure reducing machine for pressurizing fluid or reducing the pressure thereof.
The conventional crank engines are used as internal combustion engines in various fields. On the other hand, barrel type crankless engines have been devised as engines which omit crank or as improvements over crank engines [see, for example, Toru Daidoji, "Crankless Engine," Nikkan Kogyo Shinbun-Sha (May 25, 1961), P. 239]. These crankless engines are of a structure having an inclined crank pin, which is also called a Z type crank shaft.
As engines of this type there have also been developed barrel cam type and swash plate type crankless engines. But both are disadvantageous in point of durability and production because the transfer portion includes linear or point contact or the sliding velocity is too high. Therefore, they have not become popular yet. As a crankless engine which has been put to practical use there is a rotary engine (manufactured by Matsuda Co.).
As compared with the reciprocating type engines, the rotary engine is superior in point of smoothness of rotation, reduced size and weight, reduced number of parts required, and simplified structure. However, the fuel economy is poor, which is ascribable to the leakage of gas from the apex or side seal, and in this is point the rotary engine involves a serious problem.
In the reciprocating type engines available at present there are used four to five intake and exhaust valves for each cylinder to improve performance and fuel economy. But this is almost a limit.
As to reciprocating type engines, the development of a high-powered engine capable of affording smooth rotation and superior in quietness has been desired. Also in the field of air compressors and vacuum pumps using a piston it has been desired to develop products of high efficiency.
Particularly, in reciprocating type multicylinder engines having a crankshaft, there have been drawbacks. For example, the manufacturing cost is high because of a complicated shape, and it is necessary to use a number of bisplit bearings which are peculiar to the crankshaft, resulting in increase in size of the entire engine.
Besides, the increase the number of bearings gives rise to the problem that the slip loss of bearings is large, the mechanical efficiency becomes poor, and the amount of fuel consumed is increased.
Further, the material cost, forging cost and machining cost for the crank shaft are increased, and considerable time is required for a complicated machining in the crank case bearing portion, so it is now necessary to cope with the increase of the manufacturing cost.
More particularly, multicylinder engines are required for the purpose of attaining increased output and smooth rotation, and like a demand contradictory thereto, the reduction of size and weight are required.
On the other hand, it is necessary to attain both the improvement of performance and the decrease in the amount of fuel consumed. To this end, manufacturers are earnest about studies and there has been a recent tendency to increase in the number of intake and exhaust valves. But it seems that this way of doing has already reached a limit.
Under such background, various crankless engines have been devised as mentioned above, but most of them have not been put to practical use.
The following are mentioned as reasons why crankless engines have not been used practically.
(1) In many of crankless engines there is a portion in which contact surfaces are in point or linear contact as in the combination of a barrel cam and a roller, so wear out sooner to an unpractical extent.
(2) Since the sliding velocity is high, a high-speed rotation is not obtained and so it is impossible to attain the improvement of performance.
(3) On the same displacement basis, the volume of the entire engine becomes too large, resulting in increase of weight.
(4) Many of the crankless engines in question are difficult to machine and cause problems in their manufacture.
(5) The structure is too complicated, resulting in increase of cost, which is a problem when viewed from the economic point of view.